Delete node from XML file while reading it with XmlReader?

Question

I have a script that reads XML node by node using XMLReader:

$z = new XMLReader;
$z->open('xmlfile.xml');
$doc = new DOMDocument;

while ($z->read() && $z->name !== 'item');
while ($z->name === 'item')
{
    $node = simplexml_import_dom($doc->importNode($z->expand(), true));

    //I read the node here 
    print_r($node);

    //Here I want to delete it
    //////////////////////////

    //move to next node
    $z->next('item');
}

I want to delete the node from XML file after reading it to avoid reading same data multiple times when calling the script again. What is the best way to do it? Am I able to do it while reading the file?

I couldn't find the answer anywhere else.

Answer 1

XMLReader has a partner called XMLWriter. So for large XML files you read the XML file using XMLReader while writing the filtered/modified data using XMLWriter into a new file.

Expanding a part of the file into DOM allows easier reading and modifications of this part but you will need to use XMLWriter to serialize the XML structure into the new file.

I implemented features (including a collapse() method) for that into FluentDOM. Here is an usage example:

$xml = <<<'XML'
<persons>
  <person><name>Alice</name></person>
  <person><name>Bob</name></person>
  <person><name>Charlie</name></person>
</persons>
XML;

// Create the target writer and add the root element
$writer = new \FluentDOM\XMLWriter();
$writer->openUri('php://stdout');
$writer->setIndent(2);
$writer->startDocument();
$writer->startElement('persons');

// load the source into a reader
$reader = new \FluentDOM\XMLReader();
$reader->open('data://text/plain;base64,'.base64_encode($xml));

// iterate the person elements - the iterator expands them into a DOM element node
foreach (new \FluentDOM\XMLReader\SiblingIterator($reader, 'person') as $person) {
  /** @var \FluentDOM\DOM\Element $person */
  // ignore "Bob"
  if ($person('string(name)') !== 'Bob') {
    // write expanded node to the output
    $writer->collapse($person);
  }
}

$writer->endElement();
$writer->endDocument();

Output:

<?xml version="1.0"?>
<persons>
 <person>
  <name>Alice</name>
 </person>
 <person>
  <name>Charlie</name>
 </person>
</persons>